FIX: add safe navigation to serializer include conditions (#1349)

In some rare cases a post can exist without a topic

Author: SamSaffron

lib/ai_bot/entry_point.rb

@@ -140,15 +140,16 @@ def inject_into(plugin)
           :topic_view,
           :is_bot_pm,
           include_condition: -> do
-            object.personal_message && object.topic.custom_fields[TOPIC_AI_BOT_PM_FIELD]
+            object.topic && object.personal_message &&
+              object.topic.custom_fields[TOPIC_AI_BOT_PM_FIELD]
           end,
         ) { true }
 
         plugin.add_to_serializer(
           :post,
           :llm_name,
           include_condition: -> do
-            object.topic.private_message? && object.custom_fields[POST_AI_LLM_NAME_FIELD]
+            object&.topic&.private_message? && object.custom_fields[POST_AI_LLM_NAME_FIELD]
           end,
         ) { object.custom_fields[POST_AI_LLM_NAME_FIELD] }